Contact lenses in wide use today fall into two categories. First, there are the hard or rigid corneal type lenses that are formed from materials prepared by the polymerization of acrylic esters, such as polymethylmethacrylate (PMMA). Secondly, there are the gel, hydrogel or soft type of lenses made by polymerizing such monomers as 2-hydroxyethyl methacrylate (HEMA) or, in the case of extended wear lenses, made by polymerizing silicon-containing monomers or macromonomers. Solutions that wet the lenses before insertion in the eye are required for both the hard and soft types of contact lenses, although their formulations have tended to differ based on their different properties. After the contact lenses are inserted in the eye, ophthalmic solutions for rewetting, lubricating, and/or enhancing wearer comfort are sometimes applied to the eye by means of a drop dispenser.
Isotonic solutions for improving the comfort of wearing soft contact lenses by being added directly to the contact lens in the eye are known. Such solutions typically contain viscosity enhancing agents, lubricants, surfactants, buffers, preservatives, and salts. For example, U.S. Pat. No. 4,529,535 to Sherman discloses a rewetting solution that is particularly useful for rigid silicone copolymer contact lenses, including extended wear lenses. In one embodiment, the rewetting solution contains the combination of hydroxyethylcellulose, polyvinyl alcohol, and polyvinylpyrrolidone.
U.S. Pat. No. 4,786,436 to Ogunbiyi, et al. discloses a wetting solution comprising collagen and other demulcents such as hydroxylethyl cellulose, methyl cellulose, carboxymethyl cellulose, hydroxypropyl methylcellulose, hydroxylpropyl-cellulose and the like.
U.S. Pat. No. 4,748,189 to Su et al. discloses ophthalmic solutions for improving the exchange of fluid in the area outside a hydrogel contact lens in the area underneath the hydrogel contact lens, in order to permit tear exchange to occur, thereby preventing the accumulation of waste matter and debris under the lens. The solution contains a hydrogel flattening agent, for example urea, glycerin, propylene glycol, sorbitol, or an amino-ethanol. Surfactants that are useful in the solution include poloxamer and tyloxapol. Suitable lubricants include hydroxylethylcellulose, polyvinylalchol, and polyvinylpyrrolidone.
U.S. Pat. No. 5,209,865 to Winterton et al. discloses a conditioning solution for contact lenses that comprises a combination of a poloxamine and a poloxamer surfactant each having an HLB (hydrophilic-lipophilic balance) of seven or below. The solution according to the invention forms a uniform hydrophilic film on a lens surface for which proteins have very little affinity. As such, a contact lens contacted by the solution is said to have a coating that provides a prophylactic effect to the lens.
U.S. Pat. No. 5,604,189 and U.S. Pat. No. 5,773,396 to Zhang et al. disclose a composition for cleaning and wetting contact lenses comprising (i) a non-amine polyethyleneoxy-containing compound having an HLB of at least about 18, (ii) a surface active agent having cleaning activity for contact lens deposits that may have an HLB less than 18, and (iii) a wetting agent. Such compositions can include, as the wetting agent, an ethoxylated glucose derivative such as glucam, also disclosed in U.S. Pat. No. 5,401,327 to Ellis et al. Tyloxapol is a conventional surface active agent, used for example in Allergan's Complete.RTM. multipurpose solution, which agent has cleaning activity for contact-lens deposits and has an HLB less than 18.
Unlike hard lenses, the soft type of contact lenses have a tendency to bind and concentrate significantly more fluids, environmental pollutants, water impurities. Likewise, the soft type of contact lenses is more susceptible to the deposition of protein or lipids or both. Thus, the use of enzymes or equivalent protein-removing agents has been conventionally employed for weekly or daily protein removal from worn lenses. In contrast, surfactant cleaning agents in daily lens care solutions are useful for the removal of lipid or lipid-like materials from the lenses. With the advent of extended wear lenses, however, in which lenses are worn overnight and even continuously over a plurality of whole days, night and day, the lens wearers no longer have the opportunity to remove, by means of the conventional lens care solutions, the depositions that have accumulated over the day.
It would, therefore, be desirable to have a solution that could be applied to the eye that not only rewets the lens but also cleans and/or prevents the deposition of lipids until such time as the lens is removed from the eye and cleaned or disposed. However, it does not necessarily follow that cleaning agents that can be used in cleaning solutions in which contact lenses are immersed for several hours or more would be effective when applied in the form of eyedrops to a lens in the eye. In particular, cleaning agents that are designed to prevent the deposition of lipids on a lens must have an extended effect on a lens within the eye. At the same time, cleaning agents must be selected that are very safe and comfortable, especially as they would be expected to associate with the lens surfaces while in the eye.